The aim of the research proposed in this grant is to gain insight into the mechanisms used for signal transduction in the visual system using a combined molecular, genetic and physiological approach. It is expected that the results obtained from these studies will help our understanding of the basis of sensory reception and information processing in biological systems. Over the past 2-1/2 years we have concentrated our research efforts characterizing genes encoding proteins involved in the phototransduction cascade. We isolated the ninA gene (cyclophilin-homologue), a photoreceptor-cell specific protein kinase C, a Drosophila homologue of vertebrate arrestin, and a photoreceptor-cell specific dehydrogenase. We have also continued our analysis of Drosophila opsins and genetically engineered Drosophila lines that express different opsins in the R1-R6 photoreceptor cells. These experiments allowed us to examine the contribution of the various opsins to the specific functional properties of the different photoreceptor cell types. This proposal now focus our research efforts on two of these gene families: opsins and ninaA. We will: (1,2) Determine the molecular basis of spectral specificities in the opsin molecule. (3) Isolate the gene(s) encoding the opsin expressed in the central R8 photoreceptor cell class of the Drosophila compound eye, and (4) generate mutants lacking the R7 and R8 visual pigments, and characterize them molecularly and physiologically. We will also: (5) Identify the sites of expression of the ninaA gene, and generate antibodies against its gene product. (6) Generate transgenic lines overexpressing ninaA, and produce and characterize the ninaA protein in bacteria (T7 expression system) and Drosophila culture cells (Schneider cells). (7) Characterize in detail the visual physiology and biochemistry of ninaA flies and determine the psychological phenotype of wild-type flies acutely and chronically treated with CsA. (8) Construct and characterize a heat- shock inducible ninaA gene an attempt to isolate temperature sensitive alleles of ninaA. (9) Isolate other members of the ninaA gene family, and search for a putative R7 cell-specific homolog. Finally, we will study in detail those sequences which based on their patterns of expression and genetic and biochemical criteria most warrant further investigation.